package com.gitee.candy.encry;

import javax.crypto.Cipher;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

public class EncryptRSAUtils {

    private static Map<Integer, String> keyMap = new HashMap<Integer, String>();  //用于封装随机产生的公钥与私钥

    public static void main(String[] args) throws Exception {
        //生成公钥和私钥
        genKeyPair();

//        keyMap.put(0, "suylasuylasuylasuylasuylasuylasuylasuylasuylasuylasuylasuylasuylasuylasuylasuylasuylasuylasuylasuyla12345678");
//        keyMap.put(1, "candycandycandycandycandycandycandycandycandycandycandycandycandycandycandycandycandycandycandycandy12345678");
        //加密字符串
        String message = "df723820";
        System.out.println("随机生成的公钥为:" + keyMap.get(0));
        System.out.println("随机生成的私钥为:" + keyMap.get(1));
        String messageEn = encrypt(message, keyMap.get(0));
        System.out.println(message + "\n加密后的字符串为:" + messageEn);
        String messageDe = decrypt(messageEn, keyMap.get(1));
        System.out.println("还原后的字符串为:" + messageDe);


        String str = "宝剑分从磨砺出，梅花香自苦寒来";

        remotePublicKey = keyMap.get(0);

        String encrypt = encrypt(str);
        System.out.println(encrypt);
        String decrypt = decrypt(messageEn);
        System.out.println(decrypt);
    }

    /**
     * 随机生成密钥对
     *
     * @throws NoSuchAlgorithmException
     */
    public static void genKeyPair() throws Exception {
        // KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        // 初始化密钥对生成器，密钥大小为96-1024位
        keyPairGen.initialize(1024, new SecureRandom());
        // 生成一个密钥对，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();   // 得到私钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  // 得到公钥
        String publicKeyString = new String(EncryptBASE64Utils.encodeByte(publicKey.getEncoded()));
        // 得到私钥字符串
        String privateKeyString = new String(EncryptBASE64Utils.encodeByte((privateKey.getEncoded())));
        // 将公钥和私钥保存到Map
        keyMap.put(0, publicKeyString);  //0表示公钥
        keyMap.put(1, privateKeyString);  //1表示私钥
    }

    /**
     * RSA公钥加密
     *
     * @param str       加密字符串
     * @param publicKey 公钥
     * @return 密文
     * @throws Exception 加密过程中的异常信息
     */
    public static String encrypt(String str, String publicKey) throws Exception {
        //base64编码的公钥
        byte[] decoded = EncryptBASE64Utils.decode(publicKey);
        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
        //RSA加密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        String outStr = EncryptBASE64Utils.encode(cipher.doFinal(str.getBytes("UTF-8")));
        return outStr;
    }

    /**
     * RSA私钥解密
     *
     * @param str        加密字符串
     * @param privateKey 私钥
     * @return 铭文
     * @throws Exception 解密过程中的异常信息
     */
    public static String decrypt(String str, String privateKey) throws Exception {
        //64位解码加密后的字符串
        byte[] inputByte = EncryptBASE64Utils.decode(str.getBytes("UTF-8"));
        //base64编码的私钥
        byte[] decoded = EncryptBASE64Utils.decode(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));
        //RSA解密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        String outStr = new String(cipher.doFinal(inputByte));
        return outStr;
    }


    private static String remotePublicKey = "suyl";        //公钥
    private static String nativePrivateKey = "candy";        //私钥

    //加密
    public static String encrypt(String respones) {
        try {
            Cipher cipher = Cipher.getInstance("RSA");
            byte[] keyBytes = EncryptBASE64Utils.decode(remotePublicKey);
            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            PublicKey key = keyFactory.generatePublic(keySpec);
            cipher.init(Cipher.ENCRYPT_MODE, key);
            byte[] bytes = cipher.doFinal(respones.getBytes());
            String s = EncryptBASE64Utils.encode(bytes);
            return s;
        } catch (Exception e) {
            e.printStackTrace();
            return "RSA加密错误.";
        }
    }

    //解密
    public static String decrypt(String respones) {
        try {
            byte[] content = respones.getBytes();
            Cipher cipher = Cipher.getInstance("RSA");
            byte[] keyBytes = EncryptBASE64Utils.decode(nativePrivateKey);
            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            PrivateKey key = keyFactory.generatePrivate(keySpec);
            cipher.init(Cipher.DECRYPT_MODE, key);
            byte[] responseByte = cipher.doFinal(EncryptBASE64Utils.decode(content));
            String s = new String(responseByte);
            return s;
        } catch (Exception e) {
            return "RSA解密错误";
        }
    }
}
